I find Swappa a good place to buy/sell... As a seller the fees are way more reasonable than eBay. As a buyer I am more reassured by their mandatory IMEI check and ID tagged photos than Craigslist or other venues. Also some local Phone Shops might be interested, but they pay far less than you could get from a private buyer as they then need to make a profit on resale.
Yes people still want the Icon. It is a pretty upscale device.
Search: lumia icon > Swappa
Search other places for a ball park figure... Good luck.